Agree, not fixable, metal too thin so would need an expert weld job, gussetting to improve strength all of which would
ruin the temper of the remaining aluminum setting it up for further failure. FWIW had this happen on a 531 steel frame
which was twice welded and eventually failed completely when I was 20 miles out leaving only the top tube holding
the wheels together. Dicey ride home that day.
Aluminum frames are welded together then heat treated with a soak at 800+F° for an hour with slow cool thereafter
to temper the frame.
I suspect a close exam of the top tube near the headtube will show some damage there as well.